• Absolute brain oximetry: Quantitative hemodynamic responses of brain during sleep, in healthy & OSA subjects. OxiplexTS will determine % of cerebral oxygenation and absolute oxy, deoxy & total hemoglobin concentrations in brain tissue during sleep. [ Time Frame: 6 hours of sleep ] [ Designated as safety issue: No ]
  

• Apnea Hyperpnoea Index (AHI) determined during the routine sleep study. [ Time Frame: 6 hours of sleep ] [ Designated as safety issue: No ]
  

Frequency domain near-infrared spectroscopy (NIRS) offers the advantage of performing safe, non-invasive, transcranial, quantitative measurements of brain oxygenation and hemodynamics in real-time. These characteristics make NIRS the ideal tool to study physiological and pathological processes of the brain, in settings ranging from research and diagnostic laboratories to intensive care units and operating rooms.

Scientists recently developed the first commercially available absolute near-infrared oximeter, called OxiplexTS. This portable device will be used to study brain vascular autoregulatory responses (such as responses to hypoxia and hypercapnia) in persons with obstructive sleep apnea (OSA). These responses to allow for the assessment of brain vascular health. The OxiplexTS device will be beneficial in identifying persons at risk for cerebrovascular disease. Polysomnography (PSG), which is currently used to assess sleep disorders, gives important information on the function of different systems, however, it does not provide information on brain oxygenation and hemodynamics during sleep. The assessment of these factors, via NIRS, in persons with OSA is crucial because of the high prevalence of the disorder and the significant cardio/cerebrovascular health risk it represents.

The specific aim of this trial is to make OxiplexTS a clinically usable instrument, especially for research and clinical diagnosis and monitoring of sleep disorders. An additional goal is to determine the usefulness of this instrument for providing measurements in various clinical situations including intensive care management or prolonged surgical procedures, such as cardiothoracic surgery that require critical information of brain oxygenation and hemodynamics. This trial emerges from previous phase I and phase II studies which determined the feasibility of using OxiplexTS to assess brain vascular autoregulatory responses to hypoxic stimuli.

Approximately 300 participants will be recruited from a pool of healthy individuals, individuals with OSA, and volunteers undergoing overnight diagnostic or therapeutic PSG for suspected OSA.

Participants will be divided into two groups: healthy controls and persons with OSA. Both groups will undergo standard overnight sleep study or PSG.

In addition to the standard PSG (with or without Continuous Positive Airway Pressure (CPAP)), the study researchers will add the OxiplexTS—allowing them to assess brain oxygenation and hemodynamics during sleep. The hemodynamic patterns of the healthy controls will be compared to those of persons with OSA. Participants with OSA who undergo PSG/CPAP will be tested with the OxiplexTS, as well. Their PSG and PSG/CPAP data will be compared.